K. Hippolite avec Disciple of the Sword (The Crystal Stair Saga)
Rachel is an ordinary highschool girl until she gets a pair of magical katana from her mysterious teacher.
While testing out their new powers, Rachel and her friends become lost on another world. A world full of dangerous warriors, ghostly animals and ruthless dragons.
Alone, lost and without provisions, Rachel must find her way back to Earth. She must master TechMagic, a strangely addictive magic based on stances in her karate and kendo training. But there are other powers in the universe and many would subvert Rachel's companions. Her own swords have a possible connection to this Shadow Magic.
Rachel must come to deal with all this, or risk dying on a distant and alien world.